Padraig Harrington slipped eight shots behind an impressive Sean O'Hair in tough conditions at the Arnold Palmer Invitational.

Just four players broke par at blustery Bay Hill as O'Hair shot a one-over 71 and extended his overnight lead to five shots over a lurking Tiger Woods with Jason Gore, Zach Johnson (68) and Japan's Ryuji Imada six behind going into Sunday's final round.

Harrington managed just one birdie - at the par-five 12th - in a three-over par 73 that relegated him from sixth place to a share of tenth on one-over. But he is just three shots adrift of Woods and in position to rack up a confidence-boosting finish ahead of the Shell Houston Open and the Masters.

While the Dubliner drove the ball well again, missing just four fairways, he hit several wayward shots and saved par just 50 percent of the time, taking 30 putts.

A combination of thick rough and blustery conditions caused scores to soar and while Woods dropped two strokes in his last two holes, his a one-over par 71 was enough to move him from fifth to solo second on two-under.

More importantly, he is in the final group, after saving a trademark bogey at the last with a tremendous 25 foot putt.

In the rough off the tee, he sent his next into the hazard but knocked his fourth shot on the green after a drop and rolled home the putt and celebrated with fist pump as he joined O'Hair in the final group on Sunday.

"The ball was moving on the greens a little bit and it was a tough day all round," Woods said. "The golf course is playing so hard today. I had to be so patient with the round. No one is tearing this place apart.

"The wind is so blustery out there, it's hard to get your distance correct, and then once you get on the green the wind is blowing the ball on the green so you've got to allow for wind on putts from five, six feet. It's just a tough day. I am looking forward to it (tomorrow) and we'll see what happens."

O'Hair made a mockery of the tough conditions when he played his first 13 holes in two under par thanks mainly to an impressive hat-trick of birdies from the 11th. He finished bogey-bogey-par-bogey for his 71 but felt he had played almost as well as he had in shooting a 65 on Friday.

"Obviously I feel very good and very comfortable about where my game is right now," O'Hair said. "I told Paul, my caddie, when I was signing my scorecard, I bogeyed three of the last four holes, and I don't think I missed a shot.

"I just think everybody just tries to hang on for dear life. Sometimes bogey is not a bad score. I think bogey is almost par for some holes. 

"It was obviously a tough day for everybody, and I feel good that I played solid all day. The three bogeys didn't reflect on how I played the last three holes."

Gore joined Woods and O'Hair in the final threeball, despite three-putting the 18th from five feet for a 74.

O'Hair added: "As far as my pairing tomorrow, I feel very comfortable with Jason. We had a good time today. It was tough to see him finish the way he did because he played solid all day, and obviously I'm playing with Tiger, and everybody I'm sure is asking, what do you feel about that.

"I don't think I can do anything that's going to make him play worse (laughter), so I think I'm just going to focus on me and focus on my game and do what I'm doing right now, and that's just playing shot to shot and add them up at the end."

Graeme McDowell shot a three over 73 to share 24th place on three-over par.

The Ulsterman bogeyed three holes on the trot from the third, birdied the sixth from eight feet and then followed a bogey at the eighth with a birdie at the ninth to turn in two-over. 

But he could make little ground on the field on the back nine, dropping another shot at the par-three 14th to leave himself two shots outside the top-10 finish he needs to get into next week's Shell Houston Open.